This invention relates generally to the handling of printed circuit (PC) boards and is particularly directed to apparatus for the automatic, high speed transport and precise positioning of PC boards in a sequential manner.
The generally flat, board-like element upon which an electronic circuit is fabricated in many electronic apparatus is typically referred to as "the substrate", or circuit board, and is used primarily for mechanical support and insulating purposes. The conductive elements coupling circuit components are typically in the form of elongated metal foil which may be positioned on one or both sides of the circuit board. Electronic components are increasingly placed in position on the PC board by automatic, robot-like handling devices which allow for more reliable, faster PC board assembly. The PC board itself is increasingly being handled by high speed, automatic displacement and positioning apparatus in order to expedite PC board fabrication, assembly and testing.
In order to facilitate the high speed fabrication and assembly of PC boards, each PC board should be substantially planar, or flat, and should be provided with a substantially uniform array of conductive leads and apertures for receiving and mounting various electronic components on the board. Misalignment between component leads or terminals and the circuit board apertures is frequently due to the nonplanar character of the circuit board. Distortions in the flatness of the circuit board, or warpage, may arise from various factors such as irregularities in the manufacturing process, excessive heat or moisture in the circuit board storage environment, or mishandling of the circuit boards following their fabrication. Even relatively minor out-of-flatness distortions in a circuit board may preclude its high speed handling and result in misalignment between the mounting apertures in the board and the component leads to be inserted therein.
Prior art high speed PC board transport arrangements are generally capable of only handling PC boards having a very high degree of flatness and are susceptible to jamming when handling warped PC boards. Jamming of the PC board transport apparatus results in down time, thus prolonging the time required for PC board manufacturing and increasing production costs. In addition, jamming of the PC board transport apparatus generally requires intervention by production personnel and increases safety risks and the likelihood of injury in an environment where a large number of PC boards are moved at high speeds. Frequently the prior art PC board transport device itself caused distortion, breakage or damage to the PC board. For example, many PC board transport devices make use of roller arrangements which engage a planar surface of the PC board and contact printed information thereon resulting in distortion or erasure of this printed information which is relied upon by assemblers for the correct positioning of various electronic components on the PC board. In addition, prior art PC board transport devices are generally slower than other apparatus used in the processing of the PC boards, e.g., stamping and punching machinery, and thus represent a bottleneck, or delay, in the PC board assembly operation.
The present invention does not suffer from the aforementioned limitations of the prior art and thus represents an improvement thereover. The PC board feed apparatus of the present invention makes use of a belt drive arrangement for sequentially engaging each of a plurality of end-to-end arranged PC boards for linearly displacing the PC boards at high speed while maintaining the PC boards in alignment by means of a pair of spaced slots engaging respective lateral edge portions of the PC boards. A pair of idler rollers guide respective leading edge portions of the PC boards into the support rail slots, while a sensor detects misalignment of the PC boards for automatically shutting down a PC board loader mechanism to prevent jamming of the PC board feed apparatus.